from sqlalchemy import update
from sqlalchemy.ext.asyncio import AsyncSession

from app.user.models import User


async def consume_credit(user_uuid, session: AsyncSession) -> bool:
    """atomic UPDATE로 1크레딧 차감.

    WHERE credits > 0 조건으로 음수 차감 방지 + PostgreSQL 행 락.
    차감 성공 여부 반환.
    """
    result = await session.execute(
        update(User)
        .where(User.user_uuid == user_uuid, User.credits > 0)
        .values(credits=User.credits - 1)
    )
    return result.rowcount > 0